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Up to 20 percent of patients who undergo knee surgery are unhappy with the outcome. A SoCal orthopedic surgeon is trying to reduce that number, using a high-tech solution to ensure near-perfect knee procedures and better outcomes. Dr. Bruce Hensel reports for NBC4 News at 6 p.m. Monday, March 10, 2014. (Published Monday, Mar 10, 2014)

New digital mapping technology is allowing doctors to drastically improve the outcome of knee surgeries and improve the fit of new knees on patients' bodies.

Knee replacement surgery has become an increasingly common medical procedure for those in their 40s, 50s and 60s. But as many as 20 percent of all knee replacement recipients say they are unhappy with the results of their operation.

That may be because the pieces of their new artificial knee don’t fit as well as they should.

Dr. Jaime Hernandez, an orthopedic surgeon at Northridge Hospital, said knee replacements are usually done by feel with surgical instruments that aren’t designed for precision measurement. As a result, some of these surgeries could have more accurate results.

To solve this problem, Hernandez is using two high-tech imaging systems that create a GPS-like map of the knee and surrounding area and provide measurements within half a degree and half a millimeter.

"The idea is that, with this new technology, we can turn that 80 percent into a 90 percent or 95 and make this an almost perfect surgery," Hernandez said.

Using infrared signals and a special pointing device, the doctor first creates a virtual map of the area. He then receives real-time live measurements of the knee and its parts as he puts the new knee together. This helps to ensure that he is putting in the pieces as accurately as possible.

Another device then checks the pressure of the new knee before he puts in the final piece.

“The most important part of a knee replacement is to have the knee nice and snug and equal on both sides,” Hernandez explained. “You don’t want your knee too loose on one side and too tight on the other. You want it nice and snug all the way around.”

Los Angeles Police Department Officer Sandra Liddy tested Hernadez' surgery method and is currently recovering with hopes to get back on the streets as soon as she can.

"I'm in constant pain so I cannot put a uniform on right now," Liddy told NBC4 before her surgery. "Because I'm in pain, because I'm on medication, I can't get into a black and white (patrol car)."

"It needs to work, it has to work, because I need to go back to normal life," Liddy said.

NBC4 spoke with Liddy's doctor, and although she needs physical therapy, she is expected to be back at work with a pain-free knee.